This invention relates to a hydraulic brake booster for use in a vehicle.
A hydraulic brake booster is connected to a master cylinder and operated under a fluid pressure from a pressure source (such as a power pump). The hydraulic brake booster is so designed that the manipulating force of an operator acts on a valve mechanism within the booster to thereby issue an output corresponding to an input, although various types of boosters are known.
According to the present invention, there is provided a hydraulic brake booster of the type, which is connected to a master cylinder of a vehicle and functions normally as a booster of a non-stroke type (The stroke of an input shaft is determined only by opening and closing a valve mechanism incorporated therein, irrespective of the stroke of the master cylinder.), and functions to directly operate the master cylinder when a pressure source is in trouble.
The requirements for the hydraulic brake booster of the type described can be enumerated as follows:
A. Control of the output should be readily achieved and the booster provides the feeling of an output, i.e., suitable manipulating feeling to an operator. PA1 B. The booster does not require excessive shift of a pedal, upon power operation of a brake, and it should prevent such an excessive shift of the pedal. PA1 C. In the event of trouble in a pressure source, it should directly operate the master cylinder, with ease. PA1 D. The construction of the booster should be simple, and it should provide high reliability in operation.
The prior art boosters of the type described all fail to meet the above requirements.